1. Field of the Invention
This invention relates to a method and apparatus for treating nasal-oropharyngeal obstructions, sleep apnea, and related breathing disorders. More particularly, this invention relates to an improved method and a device for maintaining nasal-oropharyngeal airway patency.
2. Description of the Related Art
Sleep apnea is a sleep-related breathing disorder that is thought to affect between 1-10% of the adult population. Recent epidemiologic data indicate that 2% of women and 4% of men between the ages of 30 and 60 years meet the minimum diagnostic criteria for sleep apnea syndrome, representing more than 10 million individuals in the United States. It is a disorder with significant morbidity and mortality, contributing to increased risk of hypertension, cardiac arrhythmias, stroke, and cardiovascular death. Current treatments include nasal continuous positive airway pressure ("CPAP"), bi-level positive airway pressure ("BiPAP"), surgery, and other treatments. However, while CPAP and BiPAP are effective, up to 50% of patients discontinue treatment due to inconvenience and discomfort.
Sleep apnea is characterized by multiple respiratory pauses during sleep. These pauses, or apneas, are defined as the complete cessation of airflow in nasal and oral airways lasting at least 10 seconds. Partial reductions in airflow, known as hypopneas, are defined as the reduction of airflow in the nasal and oral airways lasting at least 10 seconds. Apneas and hypopneas result from the complete or partial obstruction of the upper airway, and can cause oxygen desaturation, arousal from sleep, or both. Any condition that interferes with airway patency can contribute to or result in the occurrence of such events. Therefore, the maintenance of upper airway patency is the primary goal of treatment of patients with sleep apnea. Upper airway patency can conveniently be achieved by maintaining nasal-oropharyngeal airway patency.
One common method for treating sleep apnea is the use of nasal continuous positive airway pressure ("CPAP") as disclosed in U.S. Pat. No. 5,065,756. Nasal CPAP is administered by means of a mechanical device that delivers pressurized room air to the nasal passage, or airway, through a nose mask that is worn by the patient. This device helps to maintain upper airway patency by means of a "pneumatic splint." (Sullivan et al., 1981, Lancet, 1, 882-865; Sanders, 1983, Chest, 83, 144-145). However, compliance with, and long-tern acceptance of, this treatment are poor. Studies have shown that between 20% and 50% of patients fail to use nasal CPAP as prescribed (Sanders, et al., 1986, Chest, 90, 330-333; Krieger & Kurtz, 1988, Europ. Respira. J., 1, 436-438; Kribbs, et al., 1993, Am Rev. Respir. Dis., 147, 887-895).
Other treatments for sleep apnea include the use of a tongue retaining device and other oral appliances (Lowe, 1994, Principles and Practice of Sleep Medicine, Philadelphia, Suanders), and surgical procedures such as uvulopalatopharyngoplasty (UPPP) and laser-assisted uvulopalatopharyngoplasty (LAUP) (Fujita, 1981, Otolaryngo. Head Neck Surg., 89, 923-934; Kamami, 1990, Acta Otorhino-laryngol Belgica, 44, 451-456). However, the efficacy of these treatments is generally poor, with significant improvement achieved in fewer than 1/3 of the patients treated.
The failure of current therapies to provide effective and tolerable treatment for sleep apnea has led to consideration of novel devices. It has been suggested that sleep apnea can be treated with the use of a nasopharyngeal tube (Nahmias & Karetzky, 1988, Chest, 94, 1142-1147; Afzelius, et al., 1981, Laryngoscope, 91, 285-291). Nasopharyngeal tube therapy has resulted in a reduction in apneas and hypopneas, decreased stage I (light) sleep, increased rapid-eye-movement (REM) sleep, and subjective improvement in daytime sleepiness.
While the apparatuses described in the prior art, for example, U.S. Pat. Nos. 5,664,567 and 4,821,715 are nasopharyngeal tubes that can be inserted into the airways of patients with sleep apnea, these devices were designed to be inserted by a physician, not a patient. These tubes are difficult to insert and are not appropriate for nightly use at home by the patient. It is desirable to further refine the method and apparatus to provide an effective, convenient, and tolerable treatment for sleep apnea.
Therefore, a need still exists for an improved upper airway patency device having greater acceptance among patients that is effective, and that may be easily inserted by patients.